Tumor cells exist in the blood of a cancer patient.
The detection of existence or non-existence of tumor cells in the circulating blood enables to judge whether to suffer from cancer, or to judge the effect of treatment to a cancer patient.
The concentration of tumor cells is very low such that only several tumor cells exist with such a low concentration among 107 to 108 cells. For example, the number of tumor cells contained in the sample of 10 ml of blood is as small as 4 to 5.
According to she method disclosed by Patent Document 1, rare cells are separated from the blood by use of magnetic panicles coupled with biologically-specific ligand which reacts specifically with rare cells (rare cell), such as circulating tumor cells; the separated rare cells are labeled, and the labeled rare cells are observed, thereby detecting the existence of rare cells and the number of rare cells.
According to the device disclosed by Patent Document 2, a blood sample treated with a fluorescent substance is pasted on a transparent slide glass, the transparent slide glass is scanned with a radiation beam so as to emit light, the light is converted into optical signals, and the optical signals are processed, thereby detecting rare substances.